The present invention relates generally to electrical power protection techniques and more particularly to a safety mechanism for shielding high voltage live switch gear elements forming part of an overall switch gear assembly from the immediate area surrounding fuses utilized to electrically protect the assembly during repair and/or replacement of the fuses.
A typical switch gear assembly for use with three-phase high voltage is disposed within its own housing along with fuses, one for each phase, which serve to electrically protect the switch gear. While the fuses are also located within the same overall housing as the switch gear, they are spaced from the switch gear so that when there is a necessity for repairing or replacing one or more of the fuses, the danger of arcing from the high-voltage switch gear is reduced. Nevertheless, there is still a possibility of electrical arcing across the live switch gear and the area surrounding each fuse. This arcing could be hazardous to an operator repairing or removing a fuse.
In view of the foregoing, it is the primary object of the present invention to provide an uncomplicated and yet reliable way of ensuring that arcing does not occur between a live switch gear component or power terminal connecting that component to a fuse and the fuse when the latter is being repaired or replaced.
A more specific object of the present is to automatically physically shield the fuse to be repaired or replaced immediately after it is disconnected from the switch gear apparatus and before an operator can reach its immediate surroundings.
As will be described in more detail hereinafter, the objectives just recited are achieved by means of the electrical protection arrangement disclosed herein. That arrangement, which is especially suitable for use in high-voltage switch gear applications, includes an electrically insulated housing containing a fuse intended for placement in circuit with the switch gear and a source of high voltage. The housing has an entry door for gaining access to the fuse and also contains means therein for disengagably connecting the fuse to a terminal outside the housing through a utility opening in the housing. The terminal is connected in circuit with the source of high voltage and switch gear. In accordance with the present invention, means are provided (1) for automatically disconnecting the fuse from its terminal and thereafter closing the utility opening sufficient to physically shield the terminal from the fuse when the entry door is opened and (2) for automatically opening the utility opening and reconnecting the fuse with the terminal when the entry door is closed. In the case where the switch gear operates on three-phase voltage, such an arrangement would be provided for each phase.